Circuit interrupter



April 10, 1956 .1. F. KEITHLEY 2,741,679

CIRCUIT INTERRUPTER Filed NOV. 12, 1952 INVENTOR. Jsepw /-T Kan/LE y BY A mews ys United States Patent O CIRCUlT INTERRUPTER Joseph F. Keithley, Cleveland Heights, Ohio Application November 12, 1952, Serial No. 319,851

15 Claims. (Cl. 200-91) The present invention relates to a circuit interrupter or chopper particularly adapted to interrupt a circuit at the rate of 1,000 times per second and higher to produce regular pulsations in a circuit, usually of a relatively low voltage. The present application is a continuationin-part of my application, Serial No. 263,236, filed December 26, 1951, and contains matter divided therefrom.

The principal object of the invention is the provision of a new and improved circuit interrupter comprising first and second contacts arranged to engage another to complete a circuit, the first contact being supported by a movable member urged in a direction to bias the contact into engagement with the second contact and having a limited rate of movement, and means to oscillate one of the contacts toward and from the other at a rate of movement substantially in excess of the rate of movement of the movable member so that the contacts are separated from each other during oscillation of the driven contact.

Another object of the invention is the provision of a circuit interrupter comprising a pair of movable contacts, one normally urged into engagement with the other and limited in its rate of movement in the direction of the other contact, and electrically actuated oscillating means to reciprocate the other contact at a rate in excess of the rate of movement of the first mentioned contact so that the engagement of the contacts is momentarily interrupted.

Another object of the invention is the provision of a new and improved chopper or interrupter for a low voltage circuit, which chopper is capable of operating at frequencies of 1000 oscillations per second and substantially higher, and which produces wave patterns which are reghaving a pair of engageable contact members, one of which may be reciprocated at relatively high frequencies, and the other of which has a relatively high mass and is normally urged to engage the first mentioned contact, and electrically actuated means to reciprocate the first mentioned contact at a frequency appreciably greater than the rate at which the second mentioned contact is capable of attaining whereby the contacts momentarily separate and the latter contact floats relative to the reciprocated contact, which is separated and reengaged therewith at the frequency at which it is driven, the floating relationship thus maintaining the desired contact position.

A further object of the invention is the provision of a chopper or interrupter of the character referred to which comprises a first contact which can be oscillated or reciprocated at any desired frequency, including 1000 cycles per second and substantially higher, and which is engaged by a second contact carried by a member urged to cause the second contact to engage the first contact, and which second contact is attached to the contact carrying member by a bufier element having low compliance and high viscosity, such as a cushion of rubber or rubber-like material, so that the natural frequency of vibration of the 2,741,679 Patented Apr. 10, 1956 second contact and its support is considerably belowthe operating frequency of the reciprocable contact. When the first mentioned contact is oscillated at the frequencies indicated, the inertia of the second contact and its carrying structure prevents the latter from following the driven contact which results in separation of the contacts during a portion of each oscillation of the driven contact. Upon reengagement of the contacts the buffer element absorbs the shock, and thereby eliminates contact bounce.

Other objects and advantages of the invention will be apparent from the following detailed description of a preferred form of the invention, reference being made to the accompanying drawings wherein Fig. l is a diagram of a circuit for recording transient voltages in a thermocouple circuit and which employs a circuit interrupter or chopper embodying the present invention;

Fig. 2 is an elevational view partly in section of the chopper; and

Fig. 3 is a fragmentary view showing certain parts of a modification of the chopper shown in Fig. 2.

Although the invention may be embodied in circuit interrupters or choppers for forming pulsations in circuits for various purposes, I have chosen to illustrate the same in connection with a system for measuring voltage fluctuations of thermocouples 10 and 10' connected in series opposition. The thermocouples may be used to measure temperature and its rapid changes in an environment in which the temperature fluctuations are too rapid to be registered by conventional recording systems. The thermocouple 10' is maintained at a predetermined temperature while thermocouple 10 is subjected to temperatures desired to be measured and the predetermined temperature mentioned is approximately the average of the temperatures to be measure. Rapid changes in temperature will of course produce a corresponding voltage change in the thermocouple circuit.

The voltage fluctuations in the thermocouple circuit are in the order of millivolts or microvolts and must be amplified considerably to drive a meter or registering instrument, and in the embodiment of the invention shown, the thermocouples are connected to the terminals 11, 12 of the input circuit of an A. C. voltage amplifier G, which input includes conductors 13, 14 and a suitable resistor 15 is interposed in the conductor 13.

A circuit interrupter or chopper C embodying the invention is connected in shunt across the input of the amplifier G and comprises two contacts 16, 17 which are operated to make and break the circuit and short the thermocouple out of the amplifier input and thereby establish pulsations in the amplifier input, the excursions of which are proportional to the instantaneous voltages in the thermocouple circuits. The amplifier G and the meter R connected therewith are described and claimed in my aforementioned application and hence the details thereof are not explained herein.

In its preferred form the chopper C comprises a base plate 20 having an electromechanical driver T attached thereto. The driver is here shown as a transducer or dynamic loud speaker motor of conventional construction and, in the form shown, it includes a frame 21 attached to the underside of the base plate 20 and has a permanent magnet 22 carried therein in registration with an opening through the base plate. A coil 23 is wound on a cylindrical member 24 which is supported between the poles of the magnet by a diaphragm 25 attached to the frame. The coil 23 is connected in the output of a conventional audio oscillator 26 capable of energizing the coil at the frequency at which it is desired to operate the chopper. Energization of the coil by the audio oscillator causes the cylinder 24 and diaphragm 25 to reciprocate at the frequency of the oscillator in a direction normal to the face of the diaphragm.

The diaphragm has a conical member 23 attached thereto, which is of a suitable light weight material, such as paper, and the outer end thereof has the contact member 17 attached thereto. The contact member 17 is preferably formed of a non oxidizing metal, such as platinum iridum, and, as an example only, is approximately /s inch in diameter and .QlS" thick. flexible lead, not shown, is utilized to connect the contact in its circuit. The mass of the contact 17 and its supporting structure is relatively small so that it may be driven at high frequencies. V

The contact 17 is engaged by the contact i6 which is in the form of a #20 gauge wire held in a rubber or rubber-like buffer block attached to one end of a beam 31. The beam 31 is pivctally supported on a pin 32 fixed to and projecting from one side of an upright or post 33 attached to the plate 20. The beam 31 is substantially counterbalanced about its pivot so that 'gravitational pull thereon is cancelled irrespective of the angular disposition of the chopper.

The beam 31 is urged counterclockwise to engage contact 16 with contact 17 by a coil spring 35 one end of which is attached to the beam and the other end of which is attached to an adjusting screw 36 by a threaded connection so that the torque which the spring exerts on the beam, and consequently the force of contact 17 on contact 16, can be finely adjusted. The force exerted by the spring to urge contactli6 to engage contact 17, is preferably about ten grams, although this force may be different for different operating frequencies, etc.

The pivot and circular motion of the moving contact beam are provided so that the beam can be counterbalanced to cancel out the gravitational pull on the beam which would otherwise upset the proper contact force upon a change of the orientation with respect to the earth.

As mentioned previously, the contact 16 is in the form of a wire, and it is preferably tipped with a non-oxidizing metal, such as platinum iridum. The buffer block 36 may be formed of rubber or any suitable material similar to rubber or a mechanical damper with compliant and viscous components. One such material is a vinyl plastic sold under the trade name of Geon. The contact is connected in its circuit by a flexible lead, not shown.

When the oscillator 26 is operating, the conical member 28 and consequently the contact 17 is oscillated according to the frequency of the oscillator, and due to the inertia of the beam 31,, contact 16 cannot move at the rate of contact 17 and the lattertherefore moves from the contact 16 during the downward movement thereof, as viewed in Fig. 2. On the upward stroke of the contact 17 it reengages the contact in but due to the low compliance and high viscosity of the butter block 30,

any tendency for the contacts to bounce is absorbed by the block. Thus a clean and regular wave voltage pattern is produced in the input of the amplifier G.

It is apparent that the force urging contact 16 to contact 17 is constant throughout the range of movement of contact 17 and beyond, and since contact 16 is movable, with its rate restricted by the inertia of the beam 31, etc., proper contact force and extent of separation of the contacts are automatically maintained in the event dimensional changes in the contact holding structures occur due to temperature or humidity variations, wear, etc. Thus the mechanism operates with a high degree of efficiency and requires but a minimum of adjustment.

In the form of the invention shown, the oscillator delivers about one watt to the transducer and the amplitude of the contact 17 is about .001 inch.

The transducer T shown drives contact 17 at a fre- I quency well above the resonance of its moving system, but other forms of transducers, such as a tuning fork or plate driven at their resonant frequencies can be used to drive contact 17, and will produce the desired amplitude of oscillation of the contact with less driving power than would be required with the chopper shown in Fig. 2.

lthough I have shown a pivoted, spring loaded beam to support the contact in, other suitable supports could be employed, such as a beam supported by a spring rather than a pivot.

In the modification of the invention shown in Fig. 3 the contact corresponding to contact if? is shown at I17 and is supported on a hat spring member 4b, one end of which is riveted or otherwise secured to a block of insulation 43 attached to the plate 24 The free end of the spring 4% is turned downwardly and attached to the upper end of the cone 2% by any suitable means, such as cement, so that the spring 49 is oscillated at the oscillation rate of the oscillator 26. The natural vibration frequency of the spring it! may be different than that at which tle oscillator is set to operate and the spring is driven at the rate desired rather than at its natural frequency. As is the case in the form shown in Fig. 2, contact to rides on contact 17 and the operation of the chopper is similar to that described with reference to the first form. By carrying'contact 17 on the spring member at} greater mechanical stability is provided for the contacts which in turn tends to produce more uniform waves.

It will be seen that by my invention I have provided a reliable and highly eificient chopper, or current interrupter, which is inexpensive to manufacture and is relatively easy to maintain in proper operating condition. The chopper provides regular wave patterns at frequencies of 10,000 cycles per second and higher.

Although I have described but two forms of the invention it is to be understood that other modifications and adaptations thereof could be employed all falling within the scope of the claims which follow.

Having thus described my invention, 1 claim:

1. A circuit interrupter comprising first and second cooperating contacts, biasing means for yieldably opposing movement of said first contact in a direction away from said second contact, the inertia of said first contact and said means limiting the rate of movement attainable by said first'contact due to the action of said biasing means, and means operable independently of the making and breaking of said contacts for vibrating one of said contacts at a rate of movement greater than the first mentioned rate of movement to make and break said contacts.

2. A circuit interrupter comprising first and second cooperating contacts, a member for carrying said first contact, means yicldably urging said member to oppose movement of said first contact away from said second contact and to bias said contacts together while in engagement, the inertia of said member and said first contact limiting the rate of movement of said member toward said second contact due to the action of said means, and means operable independently of the making and breaking of said contacts for reciprocating one of said contacts at a rate of movement in excess of the first mentioned rate of movement.

3. A circuit interrupter comprising first and second movable contacts, a pivoted member for carrying said first contact, spring means for yieldably urging the pivoted member toward the second contact whereby the first'contact is urged into engagement with the second contact when the contacts are made, means for supportingthe second contact, and driving means operable-independently of the making and breaking of said contacts for reciprocating one of said contacts toward and away from the other of said contacts, the first contact and said member having a mass and inertia such that the said spring means is unable to move the first contact toward the second contact at the rate of movement imparted to the said one contact by said driving means and said contacts breaking when the direction of movement of said one contact is reversed tOH IOVC away from the other of said contacts.

4. A circuit interrupter comprising a pair of movable contacts, means for yieldably opposing movement of one of said contacts in a direction away from the other of said contacts, said one contact having a limited rate of movement in a direction toward the other contact upon the breaking of said contacts, and means operable independently of the making and breaking of said contacts for oscillating said other contact at a rate of movement in excess of the rate of movement attainable by said one contact when said contacts are separated, said contacts making when moving in opposite directions and breaking upon reversal of the direction of movement of said other contact by said oscillating means to move the said other contact in a direction away from said one contact.

5. A circuit interrupter comprising a pair of movable contacts, means yieldably opposing movement of one of said contacts in a direction away from the other of said contacts and for causing said one contact to move toward said other contact upon the breaking of said contacts, and electromechanical means operable independently of the making and breaking of said contacts for oscillating said other contact at a rate of movement in excess of the rate of movement attainable by said one contact upon the breaking of said contacts whereby said contacts are separated during each oscillation of said other contact and made when moving in opposite directions, the first-said means urging said contacts together with a substantially uniform force throughout the range of movement of said contacts while engaged.

6. A circuit interrupter comprising a pair of movable cooperating contacts, a viscous-compliant bufier device for supporting one of said contacts, means including a member for supporting said device for yieldably urging said one contact into engagement with said other contact and causing said one contact to move toward said other contact when separated therefrom, and means for oscillating said other contact at a rate of movement in excess of that attainable by said one contact when said contacts are separated.

7. A circuit interrupter comprising a pair of movable cooperating contacts, a viscous-compliant buffer device for supporting one of said contacts, means including a member for supporting said device for yieldably urging said one contact into engagement with said other contact and causing said one contact to move toward said other contact when separated therefrom, and oscillating driving means for oscillating said other contact at a rate of movement in excess of that attainable by said one contact when said contacts are separated, said other contact being oscillated at the same frequency as said driving means.

8. A circuit interrupter comprising a pair of movable contacts, means for supporting and yieldably urging one of said contacts into engagement with the other of said contacts and causing said one contact to move toward the other contact when not in engagement therewith, said one contact and supporting means having a large mass and high inertia as compared to said other contact limiting the rate of movement of said one contact when said contacts are separated, means for oscillating said other contact at a rate of movement greater than the rate of movement allowed said one contact by the inertia of said one contact and its support to make and break said contacts during each oscillation of said other contact, said contacts separating upon the reversal of direction of said other contact to move in a direction away from said one contact and reengaging when moving in opposite directions.

9. A circuit interrupter comprising first and second movable contacts, a pivoted member for supporting the first contact for movement toward and away from the second contact, spring means for yieldably urging the pivoted member toward the second contact whereby the first contact is urged into engagement with the second contact, means supporting the second contact for reciprocation toward and away from the first contact, driving means for reciprocating the second contact toward and away from the first contact, the first contact and said member having a mass and inertia such that the first contact is unable to move independently of the second contact at the rate of movement imparted to the second contact by said driving means thereby causing said contacts to separate when the direction of movement of the second contact is reversed to move it in a direction away from the first contact.

10. A circuit interrupter comprising first and second movable contacts, a member for supporting the first contact for movement toward and away from the second contact, a viscous-compliant device intermediate the first contact and said member, means for yieldably urging said member toward the second contact whereby the first contact is urged into engagement with the second contact, means supporting the second contact for reciprocation toward and away from the first contact, driving means for reciprocating the second contact toward and away from the first Contact, the first contact and said member having a mass and inertia such that the first contact is unable to move toward the second contact at the rate of movement imparted to the second contact by said driving means thereby causing said contacts to separate when the second contact is moving in a direction away from the first contact.

ll. A circuit interrupter comprising first and second movable contacts, a member for supporting the first contact for movement toward and away from the second contact, spring means for yieldably urging the member toward the second contact whereby the first contact is urged into engagement with the second contact, means supporting the second contact for reciprocation toward and away from the first contact, electromechanical driving means for reciprocating the second contact toward and away from the first contact, the first contact and said member having a mass and inertia such that the first contact is unable to move toward the second contact at the rate of movement imparted to the second contact by said driving means thereby causing said contacts to separate upon the reversal of direction of movement of said second contact by said driving means to move said second contact in a direction away from the first contact.

12. A circuit interrupter comprising first and second movable contacts, a pivoted arm for movably supporting said first contact, spring means biasing said arm about its pivot for moving the first contact toward the second con tact and yieldably urging the first contact into engagement with the second contact when said contacts are made, said spring means causing the first contact to move toward the second contact upon the breaking of said contacts, means movably supporting the second contact, the first contact and its support having high inertia with respect to the second contact and its support means, and oscillating driving means for oscillating the second contact at the frequency of the driving means and at a rate of movement in e cess of that attainable by the first contact when moving toward the second contact whereby the second contact separates from the first contact in each oscillation when moving in a direction away therefrom and reengages when moving in a direction toward the first contact, said spring means exerting a pressure on said contacts while engaged.

13. A circuit interrupter comprising first and second movable contacts, a member for supporting the first contact for movement toward and away from the second contact, spring means for yieldably urging the member toward the second contact whereby the first contact is urged into engagement with the second contact, means supporting the second contact for reciprocating toward and away from the first contact, electromechanical driving means for oscillating the second contact toward and away from the first contact, said spring means being adapted to exert a substantially uniform pressure on the first contact to urge it into engagement with the second contact throughout the range of movement of the second contact, the first contact and said-member having mass and inertia such that the first contact is unable to move toward the second contact at the rate of movement imparted to the second contact by said driving means thereby causing said contacts to separate when the second contact is moving in a direction away from the first contact.

14. A circuit interrupter comprising first and second movable cooperating contacts, means for movably supporting the first contact, means for movably supporting and oscillating the second contact into engagement with the first contact, the first contact being engaged and driven by the second contact for a portion of each oscillation where the second contact is moving in a direction toward the first contact, biasing means for yieldably opposing the movement of the first contact by the second contact and for urging the first contact into engagementwith the second contact while being driven thereby, the first contact and its supporting means having inertia sufiicientiy large so that the second contact separates from the first contact when said means for supporting and oscillating said second contact reverses the direction of movement of said second contact to move it in a direction away from the first contact.

15. A circuit interrupter comprising first and second cooperating contactsymeans for yieldably opposing the movement ofsaid second contact in a direction away from said first contact, and-means for oscillating one of said contacts toward and-away from the other of said contacts to make said contacts when said one contact is moving toward said other contact and to break said contacts upon the reversal of direction of movement of said one contact by said driving means to move the contact in adirection away from said other contact, the inertia of the first saidmeans preventing. engagement between the contacts from being maintained upon said reversal of direction of said one contact, and the first said. means operating after separation of said contacts to move said other contact to a position where said contacts will be remade in a subsequent. cycle.

References Cited the tile of this patent UNITED STATES:PATENITS 1,817,468 Van Nostrand Aug. 4, 1931 2,114,036 Smith et a1 Apr. 12, 1938 2,518,030 Kuperus Aug. 8, 1950 2,610,995 Orsatti et al. Sept. 16, 1952 

